(1) Field of the Invention
The present invention relates to an engine running control apparatus for an outboard motor, and detailedly relates to an engine running control apparatus for controlling an outboard motor so as to prevent abrupt lowering of the engine speed thereof.
(2) Description of the Prior Art
In control of an outboard motor, when the throttle is closed abruptly while the engine is running so as to completely close the throttle valve, the engine speed lowers sharply and hence the engine may stall. To eliminate such inconveniences, spark-advance control (which is the control of delaying the ignition retard) has been carried out conventionally, so as to perform gradual reduction of the engine speed, that is, a so-called tailing, to thereby prevent the engine from stalling and to improve sailing comfortableness.
Also, in order to prevent the throttle valve from being closed abruptly, a mechanical dashpot for mechanically delaying the closing timing of the throttle valve has been attached.
However, the conventional technique of performing spark-advance control is not capable of providing the engine with a high enough torque, producing difficulties in reducing the engine speed without compromising sailing comfortableness. This problem was especially marked for four-cycle engines.
When a mechanical dashpot is used, it is difficult to match the delay action of the closing angle time from the dashpot with the action of the air control valves used for EFI and the like, which causes the engine rotation to hunt and results in an unstable operation.